1. Field of the Invention
This invention relates to remote control devices for distant manipulation and, more particularly, to remote control devices suited to be used with cameras. Still more particularly, it relates to improvements of such devices for minimization of their size.
2. Description of the Related Art
In the remote control device for distant manipulation, it has been conventional that a transmitter has its own self-contained battery made contained and this battery is used as the drive source to give off the remote control signal in the form of light or ultrasonic wave. This accommodation of the battery, however, leads to increasing the size and weight of the transmitter. Hence, its portability and handiness has is lessened.
Taking an example of the camera, the basic structure of the conventional remote control device is explained by reference to FIGS. 9 and 10. FIG. 9 shows the construction and arrangement of the elements of the unifunctional remote control transmitter using pulse-modulated infrared light as the remote control signal, and FIG. 10 shows the elements of the receiver therefore. In FIG. 9, an oscillation circuit 1 produces pulses with a modulated frequency. Its output, when a push switch 6 is on, is supplied to the base of a transistor 3 through a resistor 5. An infrared light-emitting diode 2 (hereinafter referred to as iRED 2) produces a signal light as the remote control signal. A current limiting resistor 4 protects it. The above-described electrical power source or battery for the oscillation circuit 1 and iRED 2 is indicated at 7.
In FIG. 10, on the other hand, the above-described signal light is received by a photodiode 8. A load resistor 9, a coupling capacitor 10, an amplifier 11, a detector circuit 12 for the signal component in frequency, a wave-form shaping circuit 13, a code conversion circuit 14 as an interface to the camera.
Next, the operation of such a remote control device is described by using the waveforms of FIG. 11 wherein the lines on which the waveforms are shown are labeled the same reference characters as used in FIGS. 9 and 10. The oscillation circuit 1 of FIG. 9 oscillates at an equal frequency to the modulation frequency of the remote control signal. The application of its output to the base of the transistor 3 is maintained so long as the switch 6 is pushed. During this time, the transistor 3 repeats the on-and-off operation at the modulation frequency so that the pulsated current flows to the iRED 2. Thus, the pulse-modulated infrared light is produced as the remote control signal from the iRED 2.
On the receiver side of FIG. 10, as the photodiode 8 is reverse biased to the voltage Vcc of an electrical power source through the load resistor 9, when the remote control signal arrives in it, the current which is almost proportional to the amount of light received flows to the photodiode 8. Therefore, a voltage which is almost proportional to the received amount of light is produced at the conjunction of the photodiode 8 and the resistor 9. The coupling capacitor 10 passes the alternate current component of it to the amplifier 11 therethrough. The amplifier 11 produces an output signal denoted by S.sub.1, due to the sensitivity of the photodiode 8 to not only the signal light but also the lights from the incandescent and fluorescent lamps, in such a form that the signal light appears together with noise as shown on line S.sub.1 in FIG. 11. This output S.sub.1 is applied to the detector circuit 12 which then produces an output representative only of the modulation frequency component from the transmitter of FIG. 9 in a form S.sub.2 of FIG. 11. This form is further changed to the one shown on line S.sub.3 by the wave-form shaping circuit 13.
This output S.sub.3 is processed by the code conversion circuit 14 to form a signal capable of controlling the camera.
It will be seen that the electrical power required in the prior known remote control device is supplied from two separate batteries, one of which takes its place in the interior of the transmitter, and the other in common to the receiver and the camera. The creation of a space that the first battery occupies in the housing of the device and the increase of the weight it adds have been an obstacle to improve the portability and manageability of the remote control device.